MESOSCALE PRECIPITATION DISCUSSION 0236
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
615 PM EDT WED JUN 17 2015
 
AREAS AFFECTED...CENTRAL TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 172215Z - 180315Z
 
SUMMARY...STATIONARY/BACKBUILDING/MERGING CELLS ALONG NORTH-SOUTH
SURFACE TROF/FEEDER BAND.  LOCALLY EXTREME TOTALS IN EXCESS OF 5"
ARE POSSIBLE. 

DISCUSSION...A WELL DEFINED SURFACE TROF FROM THE CENTER OF
TROPICAL DEPRESSION BILL TOWARD LAREDO IS ACTING AS A STRONG AND
DEEP MOISTURE CONVERGENCE BOUNDARY TO INITIATE DEEP CONVECTION. 
GIVEN THE TROF IT IS RELATIVELY STATIONARY WITHIN VERY CONFLUENT
LOW LEVEL FLOW...CONVECTIVE INITIATION REGIONS HAVE REMAINED
STATIONARY TOWARD THE LINE.  FURTHER SOUTH...INFLUENCE FROM
OUTFLOW BOUNDARY FROM COASTAL CONVECTION PAIRED WITH LIKELY SEA
BREEZE... IS ALLOWING FOR THE TROF TO RETROGRADE TOWARD THE WEST A
BIT OVER SOUTHERN PORTIONS OF THE TROF NEAR FROM AUS TOWARD SAT.
FURTHER NORTH THE CONFLUENCE ALONG AND EAST OF THE TROF ALLOWS FOR
TRAINING OVER A NARROW CORRIDOR FROM TRI TO AROUND ACT.  IT IS
EAST OF THE TROF THAT CELLS CAN TAP AXIS OF HIGHER INSTABILITIES
RANGING FROM 1000 J/KG IN THE NORTH TO 3000 J/KG NEAR SAT. 
ADDITIONALLY THESE CELLS ARE ORIENTED ON THE WESTERN EDGE OF THE
DEEPEST MOISTURE IN EXCESS OF 2" PER GPS NETWORK.  WV LOOP AS WELL
AS LAYERED TPW SUGGEST THAT ADDITIONAL UPPER (ABOVE 300MB) AND
LOWER LEVEL (850MB) MOISTURE IS INCREASING RELATIVELY SPEAKING
INTO THE ENTIRE BAND.  THIS ALONG WITH STRONG CONVERGENCE/FLUX
SHOULD ALLOW FOR HIGH RAINFALL EFFICIENCY WITH THESE CELLS WITH
RATES TO 2.5-3"/HR LIKELY. 

HI-RESOLUTION CONVECTIVE ALLOWING MODELS STRONGLY POINT TO THIS
SCENARIO...WITH HIGHER RAINFALL SIGNALS WITHIN THE BAND FROM TPL
TO TRI AS IT TRAINS NEARLY OVER THE SAME AREAS FOR THE NEXT FEW
HOURS WITH TOTALS IN THE 3-5" RANGE.  WHILE FURTHER SOUTH CELLS
ARE MORE WIDELY SCATTERED...GUIDANCE SHOWS THIS SIMILAR PATTERN
WITH POCKETS OF 3-5" AS WELL.  HOWEVER...GIVEN CURRENT OBSERVED
RAINFALL RATES EXPECT THIS MAY BE UNDERDONE WITH LOCALLY EXTREME
TOTALS BEING POSSIBLE.    

GALLINA

ATTN...WFO...CRP...EWX...FWD...HGX...SHV...SJT...

ATTN...RFC...ABRFC...LMRFC...WGRFC...

LAT...LON   33629636 32999552 31439593 28849784 28559959 
            29489990 30239939 31269799 32349666